In this prospective case-control study, we enrolled 157 patients with glaucoma (mean age 67±11, 50% female) and 71 controls (mean age 60±10, 69% female). Using a pupillometer, we recorded and analyzed pupillary responses to various stimulus patterns (full field, superonasal and inferonasal quadrant arcs). We compared the responses between the two eyes, compared responses to superonasal and inferonasal stimuli within each eye, and calculated the absolute PLR value of each individual eye. We assessed the relationship between PLR, VF and RNFL using Pearson correlation coefficients. For analyses performed at the level of individual eyes, we used mixed effects multi-level modeling to account for between-eye correlations within individuals.

Results

Persons with glaucoma had a more asymmetric pupil response between the two eyes (p<0.001), between superonasal and inferonasal field within the same eye (p=0.014), and also had a smaller amplitude, slower velocity and longer latency of pupil response as compared to controls (all p<0.001). For every 0.3 log unit difference in between-eye asymmetry of PLR there was an average 2.3 dB difference in VF mean deviation (R2=0.62, p<0.001, Figure 1) and a 3.7μm difference in RNFL thickness between the two eyes (R2=0.34, p<0.001, Figure 2). Greater VF damage and a thinner RNFL for each individual eye were associated with a smaller response amplitude, slower velocity, and longer time to peak constriction and dilation (all p<0.001 after adjusting for age and gender). However, within-eye asymmetry of PLR between superonasal and inferonasal stimulation was not associated with within-eye differences of corresponding locations in VF or RNFL.

Conclusions

When measured precisely the PLR is strongly correlated with visual field functional testing and measurements of RNFL thickness. Quantitative pupillography may have a role in the diagnosis and management of optic neuropathies.